Astanga Hrudaya
शस्त्रेण ताः परिहरेच्चतस्रो मांसरज्जवः। चतुर्दशास्थिसङ्ग़ाताः, सीमन्ता द्विगुणा नव॥१५॥
there are four mamsa rajju (muscular ropes), fourteen asthisanghata (confluence of bones), simanta (border lines, dividing lines, demarcations) are twice of nine i.e. eighteen in number
english translation